1. Field of the Invention
The present invention relates to a developing unit in a wet electrophotographic printer, and more particularly, to an apparatus for preventing toner from settling in a developer storage vessel.
2. Description of the Related Art
A developing unit in a wet electrophotographic printer, as shown in FIG. 1, includes a storage vessel 11 for storing a developer I, and a developing portion 12 for developing electrostatic latent images formed on a photosensitive means such as a photosensitive belt 14. The developer I used in such electrophotographic printers is a mixture comprising a powder toner of a predetermined color and a liquid carrier.
During a print operation, a pump 15 causes the developer I in the storage vessel 11 to flow through a developer supplier 13. Accordingly, the developer I is supplied to the developing portion 12, where it is applied to the photosensitive belt 14 using a developing roller 121. The developer I which does not adsorb onto the photosensitive belt 14 returns to the storage vessel 11 via a recovery tube 16.
If the developer I in the storage vessel 11 becomes stagnant, the powder toner separates from the liquid carrier and settles onto the floor of the storage vessel 11. Such a stagnant condition exists, for example, when printing is not performed for an extended period of time. Conventionally, therefore, the developing unit includes an apparatus for mixing the developer within the storage vessel 11, thereby avoiding a stagnated condition. Specifically, a first magnet 18a is rotatably installed under the storage vessel 11. A driving motor 17 imparts rotational movement to the first magnet 18a. A second magnet 18b is installed on the bottom of the storage vessel 11. The second magnet 18b rotates, due to magnetic affects, along with the rotational movements of the first magnet 18a. A blade 19 coupled to the second magnet 18b stirs the developer I in the storage vessel 11 to prevent the toner from separating from the liquid carrier.
A toner intake 111 and a carrier intake 112 are installed in the storage vessel 11 to provide the developer I with a constant mixture ratio.
Although generally thought to be acceptable, conventional apparatus are not without shortcomings. In particular, since the second magnet 18b must be rotatably installed inside the storage vessel 11, assembly of the apparatus is difficult. Also, it is difficult to repair and/or replace the second magnet 18b.